Objectives: (1) The site where DNA synthesis begins on the adenovirus DNA is being investigated using isolated half molecules and pieces of DNA generated by restriction endonucleases. (2) The assembly of adenovirus proteins from subunits is being studied in temperature sensitive mutants of adenovirus type 5 and wild type adenovirus type 2 at elevated temperature. (3) The mechanism of action of camptothecin, an inhibitor of nucleic acid synthesis, is under investigation both in viral infected and uninfected cultured mammalian cells.